Violence in Iraq dropped further during the summer although security gains remain "reversible and uneven," with the main threats coming from Iranian-backed militias and the Shiite-led Iraqi government's slow integration of volunteer Sunni fighters, according to a Pentagon report released yesterday.

Potential is growing, moreover, for politically driven violence as ethnic, tribal and religious groups vie for influence in advance of provincial elections planned in coming months, according to the congressionally mandated quarterly Pentagon report on security in Iraq.

Overall, civilian deaths across Iraq declined 77 percent in the three months from June to August compared with the same period a year ago, with June recording the lowest monthly death rate on record since the war began, the report said. Sectarian killings increased slightly in July and August, but they remained 96 percent lower than for the same period in 2007, it said. For example, there were 26 ethno-sectarian deaths in Baghdad in the summer months -- in contrast to more than 1,200 in the same period last year.

Total attacks and other security incidents remained at their lowest levels since early 2004, even as the U.S.-led coalition withdrew thousands of troops. "Security incidents are now at the lowest levels in over four-and-a-half years, instilling in the Iraqi people a sense of normalcy that permits them to engage in personal, religious, and civic life without an inordinate threat of violence," the report said.

Nevertheless, the report voiced concern over several problems that could rekindle violence among competing groups and upset the recent progress on security.

One major concern is the Iraqi government's delays in reintegrating the nearly 100,000 predominantly Sunni volunteer fighters known as the Sons of Iraq into the army, police or other jobs, it said. "Integration of the SOI remains critical to providing stable security," the Pentagon report said, adding that the Sunni volunteer forces suffer from "low-level infiltration by insurgent groups," including the main Sunni insurgent group known as al-Qaeda in Iraq.

Tensions between the government and Sunni volunteers are particularly high in Diyala province, where the Sunni population is fearful that the government is using military operations ostensibly aimed at al-Qaeda in Iraq as a pretext to "arrest, intimidate, or kill moderate Sunnis and SOI groups who are otherwise interested in participating in the political processes," the report found.

Diyala, a demographically mixed Sunni and Shiite province east of Baghdad, remains one of the most violent in Iraq and one where al-Qaeda continues to conduct suicide attacks and "enjoys some freedom of movement" in mountains and rural areas, according to the report.

Iranian influence in funding, training and arming militias is "the most significant threat to long-term stability in Iraq," the report found. It said many leaders of the Iranian-backed "special groups" fled to Iran after Iraqi and U.S. military operations began last spring in strongholds such as Basra, Baghdad and Maysan province. Those operations "inflicted heavy losses" on the special groups and the Mahdi Army militia of Shiite cleric Moqtada al-Sadr, the report said, noting that one U.S. brigade killed more than 770 militia members and special-group fighters.

The report also said some Mahdi Army fighters are ignoring a call by Sadr to join a political movement and are instead forming "new, more lethal" special groups, which continue to receive Iranian aid.

"Whether recent security gains are long-term will depend, in part, on how these issues continue to develop," the report said.

The report warned that violence could increase in various localities in the run-up to provincial elections. For example, it said Sunni insurgents in Baghdad could increase attacks if the Sunni populace believes its election prospects are being "hindered" by the Iraqi government. In the western province of Anbar, fighting could escalate between militias controlled by the two main political parties, the report said.